IEEE 1076 standard.VHDL language reference manual.2000

IEEE

Std 1076, 2000 Edition

IEEE STANDARD VHDL

Extended digit

Replacement when the base specifier is

Replacement when the base specifier is

265

'O'

'X'

0

000

0000

1

001

0001

2

010

0010

3

011

0011

270

4

100

0100

5

101

0101

6

110

0110

7

111

0111

8

(illegal)

1000

275

9

(illegal)

1001

A

(illegal)

1010

B

(illegal)

1011

C

(illegal)

1100

D

(illegal)

1101

280

E

(illegal)

1110

F

(illegal)

1111

182

Copyright © 2000 IEEE. All rights reserved.

IEEE

LANGUAGE REFERENCE MANUAL

Std 1076, 2000 Edition

Example:

B"1111_1111_1111"

--

Equivalent to the string literal "111111111111".

285

X"FFF"

-- Equivalent to B"1111_1111_1111".

O"777"

-- Equivalent to B"111_111_111".

X"777"

--

Equivalent to B"0111_0111_0111".

assert

c1'LENGTH = 12 and

c2'LENGTH = 12 and

295

c3 = "111111111";

--

two or more consecutive lines.

305 -----------

The first two hyphens start the comment.

Copyright © 2000 IEEE. All rights reserved.

183

IEEE

Std 1076, 2000 Edition

IEEE STANDARD VHDL

310

abs

file

nand

select

access

for

new

severity

after

function

next

signal

alias

nor

shared

all

generate

not

sla

315

and

generic

null

sll

architecture

group

sra

array

guarded

of

srl

assert

on

subtype

attribute

if

open

320

impure

or

then

begin

in

others

to

block

inertial

out

transport

body

inout

type

buffer

is

package

325

bus

port

unaffected

label

postponed

units

case

library

procedural

until

component

linkage

procedure

use

configuration

literal

process

330

constant

loop

protected

variable

pure

disconnect

map

wait

downto

mod

range

when

record

while

335

else

reference

with

elsif

register

end

reject

xnor

entity

rem

xor

exit

report

340

return

rol

ror

184

Copyright © 2000 IEEE. All rights reserved.

IEEE

LANGUAGE REFERENCE MANUAL

Std 1076, 2000 Edition

360

are replaced.

Copyright © 2000 IEEE. All rights reserved.

185

IEEE

Std 1076, 2000 Edition

IEEE STANDARD VHDL

186

Copyright © 2000 IEEE. All rights reserved.

IEEE

LANGUAGE REFERENCE MANUAL

Std 1076, 2000 Edition

15

T'LEFT

Kind:

Value.

Prefix:

Any scalar type or subtype T.

Result Type:

Same type as T.

Result:

The left bound of T.

20

T'RIGHT

Kind:

Value.

Prefix:

Any scalar type or subtype T.

Result Type:

Same type as T.

Result:

The right bound of T.

25

T'HIGH

Kind:

Value.

Prefix:

Any scalar type or subtype T.

Result Type:

Same type as T.

Result:

The upper bound of T.

30

T'LOW

Kind:

Value.

Prefix:

Any scalar type or subtype T.

Result Type:

Same type as T.

Result:

The lower bound of T.

Copyright © 2000 IEEE. All rights reserved.

187

188

Copyright © 2000 IEEE. All rights reserved.

IEEE

LANGUAGE REFERENCE MANUAL

Std 1076, 2000 Edition

T'VALUE(X)

Kind:

Function.

Prefix:

Any scalar type or subtype T.

Parameter:

An expression of type String.

80

Result Type:

The base type of T.

Result:

The value of T whose string representation (as defined in

Clause 13) is given by the parameter. Leading and trailing

whitespace is allowed and ignored. If T is a numeric type or

subtype, the parameter may be expressed either as a decimal

85

literal or as a based literal. If T is a physical type or subtype,

the parameter may be expressed using a string representation of

any of the unit names of T, with or without a leading abstract

literal. The parameter must have whitespace between any

abstract literal and the unit name. The replacement characters

90

of 13.10 are allowed in the parameter.

Restrictions:

It is an error if the parameter is not a valid string representation

of a literal of type T or if the result does not belong to the sub-

type implied by T.

T'POS(X)

95

Kind:

Function.

Prefix:

Any discrete or physical type or subtype T.

Parameter:

An expression whose type is the base type of T.

Result Type:

universal_integer.

Result:

The position number of the value of the parameter.

100

T'VAL(X)

Kind:

Function.

Prefix:

Any discrete or physical type or subtype T.

Parameter:

An expression of any integer type.

Result Type:

The base type of T.

105

Result:

The value whose position number is the universal_integer

value corresponding to X.

Restrictions:

It is an error if the result does not belong to the range T'LOW

to T'HIGH.

T'SUCC(X)

110

Kind:

Function.

Prefix:

Any discrete or physical type or subtype T.

Parameter:

An expression whose type is the base type of T.

Result Type:

The base type of T.

Result:

The value whose position number is one greater than that of the

115

parameter.

Restrictions:

An error occurs if X equals T'HIGH or if X does not belong to

the range T'LOW to T'HIGH.

Copyright © 2000 IEEE. All rights reserved.

189

IEEE

Std 1076, 2000 Edition

IEEE STANDARD VHDL

T'PRED(X)

Kind:

Function.

120

Prefix:

Any discrete or physical type or subtype T.

Parameter:

An expression whose type is the base type of T.

Result Type:

The base type of T.

Result:

The value whose position number is one less than that of the

parameter.

125

Restrictions:

An error occurs if X equals T'LOW or if X does not belong to

the range T'LOW to T'HIGH.

T'LEFTOF(X)

Kind:

Function.

Prefix:

Any discrete or physical type or subtype T.

130

Parameter:

An expression whose type is the base type of T.

Result Type:

The base type of T.

Result:

The value that is to the left of the parameter in the range of T.

Restrictions:

An error occurs if X equals T'LEFT or if X does not belong to

the range T'LOW to T'HIGH.

135

T'RIGHTOF(X)

Kind:

Function.

Prefix:

Any discrete or physical type or subtype T.

Parameter:

An expression whose type is the base type of T.

Result Type:

The base type of T.

140

Result:

The value that is to the right of the parameter in the range of T.

Restrictions:

An error occurs if X equals T'RIGHT or if X does not belong to

the range T'LOW to T'HIGH.

A'LEFT [(N)]

Kind:

Function.

145

Prefix:

Any prefix A that is appropriate for an array object, or an alias

thereof, or that denotes a constrained array subtype.

Parameter:

A locally static expression of type universal_integer, the value

of which must not exceed the dimensionality of A. If omitted, it

defaults to 1.

150

Result Type:

Type of the left bound of the Nth index range of A.

Result:

Left bound of the Nth index range of A. (If A is an alias for an

array object, then the result is the left bound of the Nth index

range from the declaration of A, not that of the object.)

A'RIGHT [(N)]

155

Kind:

Function.

Prefix:

Any prefix A that is appropriate for an array object, or an alias

thereof, or that denotes a constrained array subtype.

Parameter:

A locally static expression of type universal_integer, the value

of which must not exceed the dimensionality of A. If omitted, it

160

defaults to 1.

Result Type:

Type of the Nth index range of A.

Result:

Right bound of the Nth index range of A. (If A is an alias for an

array object, then the result is the right bound of the Nth index

range from the declaration of A, not that of the object.)

190

Copyright © 2000 IEEE. All rights reserved.

IEEE

LANGUAGE REFERENCE MANUAL

Std 1076, 2000 Edition

165

A'HIGH [(N)]

Kind:

Function.

Prefix:

Any prefix A that is appropriate for an array object, or an alias

thereof, or that denotes a constrained array subtype.

Parameter:

A locally static expression of type universal_integer, the value

170

of which must not exceed the dimensionality of A. If omitted, it

defaults to 1.

Result Type:

Type of the Nth index range of A.

Result:

Upper bound of the Nth index range of A. (If A is an alias for

an array object, then the result is the upper bound of the Nth

175

index range from the declaration of A, not that of the object.)

A'LOW [(N)]

Kind:

Function.

Prefix:

Any prefix A that is appropriate for an array object, or an alias

thereof, or that denotes a constrained array subtype.

180

Parameter:

A locally static expression of type universal_integer, the value

of which must not exceed the dimensionality of A. If omitted, it

defaults to 1.

Result Type:

Type of the Nth index range of A.

Result:

Lower bound of the Nth index range of A. (If A is an alias for

185

an array object, then the result is the lower bound of the Nth

index range from the declaration of A, not that of the object.)

A'RANGE [(N)]

Kind:

Range.

Prefix:

Any prefix A that is appropriate for an array object, or an alias

190

thereof, or that denotes a constrained array subtype.

Parameter:

A locally static expression of type universal_integer, the value

of which must not exceed the dimensionality of A. If omitted, it

defaults to 1.

Result Type:

The type of the Nth index range of A.

195

Result:

The range A'LEFT(N) to A'RIGHT(N) if the Nth index range

of A is ascending, or the range A'LEFT(N) downto

A'RIGHT(N) if the Nth index range of A is descending. (If A is

an alias for an array object, then the result is determined by the

Nth index range from the declaration of A, not that of the

200

object.)

A'REVERSE_RANGE [(N)]

Kind:

Range.

Prefix:

Any prefix A that is appropriate for an array object, or an alias

thereof, or that denotes a constrained array subtype.

205

Parameter:

A locally static expression of type universal_integer, the value

of which must not exceed the dimensionality of A. If omitted, it

defaults to 1.

Result Type:

The type of the Nth index range of A.

Result:

The range A'RIGHT(N) downto A'LEFT(N) if the Nth index

210

range of A is ascending, or the range A'RIGHT(N) to

A'LEFT(N) if the Nth index range of A is descending. (If A is

an alias for an array object, then the result is determined by the

Nth index range from the declaration of A, not that of the

object.)

Copyright © 2000 IEEE. All rights reserved.

191